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Biomedical subjects

Michael S Lee

Publications and source records attributed to Michael S Lee.

At least 19 recordsLinked to original sources
PubMed2007

Stent fracture associated with drug-eluting stents: clinical characteristics and implications.

OBJECTIVE: To evaluate the clinical characteristics and implications of stent fracture in drug-eluting stents. BACKGROUND: Approximately 2.5 million drug-eluting stents are implanted every year worldwide. In 10 randomized controlled trials involving 2,602 patients, no incidence of stent fracture was recognized or reported. METHODS: From April 2003 to December 2005, 2,728 patients underwent drug-eluting stenting. The angiograms of all 530 patients who underwent repeat angiography were analyzed to identify the presence of stent fracture. We then documented the incidence of adverse events associated with drug-eluting stent fracture and systematically analyzed the clinical, procedural, and structural factors, which might predispose to stent fracture. RESULTS: Stent fracture was identified in 10 patients. None of these fractures were detectable at the time of stent placement. The median time interval from stent implantation to detection of fracture at repeat angiography was 226 days (range, 7-620 days). Adverse clinical outcomes associated with stent fracture occurred in 7 patients (6 patients had binary restenosis and 1 patient had stent thrombosis), all necessitating repeat intervention. Analysis of potential predisposing clinical, procedural, and structural factors revealed that 4 patients had excessive tortuosity in the proximal segment, and overlapping stents were used in 5 cases. All fractures occurred in sirolimus-eluting stents. CONCLUSIONS: Stent fracture may represent a new potential mechanism of restenosis and stent thrombosis in drug-eluting stents. Predisposing clinical and procedural factors may be vessel tortuosity and use of overlapping stents. The most important predisposing factor, however, may be stent structure, since all fractures occurred in sirolimus-eluting stents.

Adult↗
PubMed2006

Nonarteritic anterior ischemic optic neuropathy and 'visual field defects' following vitrectomy: could they be related?

BACKGROUND: Visual field defects after uncomplicated vitrectomy have been reported but poorly explained. We describe two cases of nonarteritic anterior ischemic optic neuropathy (NAION) observed following vitrectomy. We also reviewed the literature for cases of post-vitrectomy visual field defects for evidence of optic nerve damage. METHODS: Two patients developed optic disc edema and features of an optic neuropathy after uncomplicated vitrectomy for macular hole and epiretinal membrane. A systematic literature search was conducted to obtain prior reports of visual field defects or ischemic optic neuropathy following vitrectomy. Additional studies were identified from the bibliographies of the retrieved articles. RESULTS: The incidence of visual field defects following vitrectomy has varied from 1-71% across all studies. Overall, we found 160 (14.5%) cases of unexplained visual field defects following vitrectomy out of 1,104 patients. Of these, 31 eyes (19.4%) have shown some sign of optic nerve damage following vitrectomy, including pallor in 29 eyes, relative afferent pupillary defect in eight eyes, and intrapapillary hemorrhage in two eyes. CONCLUSIONS: NAION may develop following vitrectomy. "Visual field defects" following vitrectomy are common and many of the involved eyes demonstrate evidence of optic nerve damage, some of which may have represented NAION.

Aged↗
PubMed2006

Advances in methods and algorithms in a modern quantum chemistry program package.

Advances in theory and algorithms for electronic structure calculations must be incorporated into program packages to enable them to become routinely used by the broader chemical community. This work reviews advances made over the past five years or so that constitute the major improvements contained in a new release of the Q-Chem quantum chemistry package, together with illustrative timings and applications. Specific developments discussed include fast methods for density functional theory calculations, linear scaling evaluation of energies, NMR chemical shifts and electric properties, fast auxiliary basis function methods for correlated energies and gradients, equation-of-motion coupled cluster methods for ground and excited states, geminal wavefunctions, embedding methods and techniques for exploring potential energy surfaces.

Algorithms↗
PubMed2006

Anterior ischemic optic neuropathy after uncomplicated scleral buckling surgery.

BACKGROUND: To report a case of non-arteritic anterior ischemic optic neuropathy (NAION) observed after uncomplicated scleral buckle placement. METHODS: A 57-year-old man presented with a rhegmatogenous retinal detachment of the left eye. He underwent uncomplicated scleral buckle placement and C3F8 injection. Perioperative intraocular pressures were normal. RESULTS: On postoperative day 24, fundus examination revealed swelling of the left optic nerve and features of an optic neuropathy (visual field defect, relative afferent pupillary defect). Fluorescein angiography did not reveal delayed choroidal filling. Review of systems and laboratory investigations were not consistent with giant cell arteritis. CONCLUSIONS: Non-arteritic anterior ischemic optic neuropathy may develop after uncomplicated scleral buckling surgery.

Fluorocarbons↗
PubMed2006

Comparison of coronary artery bypass surgery with percutaneous coronary intervention with drug-eluting stents for unprotected left main coronary artery disease.

OBJECTIVES: This study evaluated the clinical outcomes of consecutive, selected patients treated with coronary artery bypass graft (CABG) surgery or percutaneous coronary intervention (PCI) with drug-eluting stents (DES) for unprotected left main coronary artery (ULMCA) disease. BACKGROUND: Although recent data suggest that PCI with DES provides better clinical outcomes compared to bare-metal stenting for ULMCA disease, there is a paucity of data comparing PCI with DES to CABG. METHODS: Since April 2003, when DES first became available at our institution, 123 patients underwent CABG, and 50 patients underwent PCI with DES for ULMCA disease. RESULTS: High-risk patients (Parsonnet score >15) comprised 46% of the CABG group and 64% of the PCI group (p = 0.04). The 30-day major adverse cardiac and cerebrovascular event (MACCE) rate for CABG and PCI was 17% and 2% (p < 0.01), respectively. The mean follow-up was 6.7 +/- 6.2 months in the CABG group and 5.6 +/- 3.9 months in the PCI group (p = 0.26). The estimated MACCE-free survival at six months and one year was 83% and 75% in the CABG group versus 89% and 83% in the PCI group (p = 0.20). By multivariable Cox regression, Parsonnet score, diabetes, and CABG were independent predictors of MACCE. CONCLUSIONS: Despite a higher percentage of high-risk patients, PCI with DES for ULMCA disease was not associated with an increase in immediate or medium-term complications compared with CABG. Our data suggest that a randomized comparison between the two revascularization strategies for ULMCA may be warranted.

Aged↗
PubMed2006

Antiplatelet and anticoagulant therapy in patients with giant cell arteritis.

OBJECTIVE: Vision loss and cerebrovascular accidents often complicate giant cell arteritis (GCA). Antiplatelet and anticoagulant therapy reduce the risk of stroke in other populations. We sought to determine whether antiplatelet or anticoagulant therapy reduces ischemic complications in patients with GCA. METHODS: A retrospective chart review for patients with GCA was conducted. Included patients fulfilled modified 1990 American College of Rheumatology criteria for GCA. Collected information included demographic data, dates of antiplatelet or anticoagulant use, vision loss or stroke, and presence of bleeding complications and cerebrovascular risk factors. RESULTS: A total of 143 patients were included with a mean followup period of 4 years. The cohort included 109 women (76%) and 34 men (24%) with a mean age of 71.8 years. A total of 104 patients (73%) had a biopsy-proven diagnosis. Eighty-six patients (60.1%) had received long-term antiplatelet or anticoagulant therapy, including 18 (12.6%) who did not start therapy until after an ischemic event had occurred. Antiplatelet agents or anticoagulants were not used in 57 patients (39.9%). Overall, 11 of 68 patients (16.2%) had an ischemic event while receiving antiplatelet or anticoagulant therapy, compared with 36 of 75 patients (48.0%) not receiving such therapy (P < 0.0005). Univariate analysis failed to show a statistical difference between groups in regard to cerebrovascular risk factors, age, sex, or biopsy-proven diagnosis. Bleeding complications occurred in 2 patients receiving aspirin, 1 patient receiving warfarin, and 5 patients who did not receive anticoagulant or antiplatelet therapy. CONCLUSION: Antiplatelet or anticoagulant therapy may reduce the risk of ischemic events in patients with GCA. An increased risk of bleeding complications was not observed.

Aged↗
PubMed2006

Coronary sinus is dilated and outwardly displaced in patients with mitral regurgitation: quantitative angiographic analysis.

OBJECTIVES: Our aim was to define the anatomy of the coronary sinus (CS) by venography. These measurements are essential in the selection of physical characteristics of percutaneous annuloplasty devices for mitral regurgitation (MR). BACKGROUND: Clinical trials of percutaneous annuloplasty of the CS for MR are now underway. Although the CS is in close proximity to the mitral annulus, there is as yet no published quantitative data defining the magnitude of change in CS dimensions in MR, and how these changes might reflect the magnitude of MR. METHODS: We studied 57 patients (27 patients with MR and 30 patients with no MR) who were referred for cardiac resynchronization therapy and underwent CS venography. Echocardiography was used to assess the degree of MR, cardiac dimensions, and right heart filling pressures. The diameter of the ostial and proximal CS and perimeter of the CS-great cardiac vein (GCV) were assessed by quantitative coronary analysis. RESULTS: Patients with MR had a larger ostial CS diameter (19.4+/-3.9 mm vs. 16.9+/-4.6 mm, P=0.02) and proximal CS diameter (8.2+/-1.7 mm vs. 7.4+/-2.3 mm, P=0.05) and larger CS-GCV perimeter (104.4+/-15.6 mm vs. 86.5+/-15.3 mm, P=0.005) compared with patients with no MR. The CS-GCV perimeter is positively correlated to the severity of MR (P=0.02) and pulmonary artery pressure (r=0.32, P<0.05). CONCLUSIONS: Patients with MR have a dilated and outward displacement of the CS. The CS-GCV perimeter is positively correlated with the degree of MR and pulmonary artery pressure.

Analysis of Variance↗
PubMed2006

Percutaneous left ventricular support devices.

Patients undergoing percutaneous coronary intervention (PCI) who have severely compromised left ventricular systolic function and complex coronary lesions including multivessel disease, left main disease, or bypass graft disease are at higher risk of adverse outcomes from hemodynamic collapse. The TandemHeart percutaneous left ventricular assist device and the Impella Recover LP 2.5 System may provide rapid circulatory support in high-risk PCI patients and in those who have cardiogenic shock. Identification of patients who are at high risk for severe hemodynamic compromise and most likely to benefit from mechanical circulatory support is crucial to derive the most benefit from this therapy. Multicenter randomized clinical trials are needed to clearly define the role of these two devices in providing circulatory support in a variety of clinical settings.

Cardiac Output, Low↗
PubMed2006

Comatic aberration as a cause of monocular diplopia.

Three patients (5 eyes) presented with complaints of monocular diplopia and no history of ocular trauma or surgery. The patients had comprehensive neuroophthalmic evaluation including manifest refraction, anterior segment and dilated fundus examination, and corneal topography. All patients also had wavefront analysis using the LADARWave system (Alcon). Two patients (4 eyes) also had hard contact lens overrefraction. The patients had a normal initial examination including corneal topography. One patient (2 eyes) did not experience resolution of diplopia with pinhole. No eye improved with manifest refraction or hard contact lens overrefraction. However, each patient had a significant amount of coma on wavefront analysis. Moreover, eyes with horizontal diplopia had horizontal coma and eyes with vertical diplopia had vertical coma as measured with the wavefront device. Higher-order optical aberrations such as coma may be associated with monocular diplopia. Wavefront technology may be useful in the workup of monocular diplopia.

Corneal Topography↗
PubMed2006

Bivalirudin in acute coronary syndromes and percutaneous coronary intervention.

The standard of care for patients with acute coronary syndrome is antithrombotic and antiplatelet therapies along with early percutaneous coronary intervention. Because of the limitations of heparin, there has been an interest in direct thrombin inhibitors, such as bivalirudin, which is now the anticoagulant of choice in percutaneous coronary intervention.

Acute Disease↗
PubMed2005

Calculation of absolute protein-ligand binding affinity using path and endpoint approaches.

A comparative analysis is provided of rigorous and approximate methods for calculating absolute binding affinities of two protein-ligand complexes: the FKBP protein bound with small molecules 4-hydroxy-2-butanone and FK506. Our rigorous approach is an umbrella sampling technique where a potential of mean force is determined by pulling the ligand out of the protein active site over several simulation windows. The results of this approach agree well with experimentally observed binding affinities. Also assessed is a commonly used approximate endpoint approach, which separately estimates enthalpy, solvation free energy, and entropy. We show that this endpoint approach has numerous variations, all of which are prone to critical shortcomings. For example, conventional harmonic and quasiharmonic entropy estimation procedures produce disparate results for the relatively simple protein-ligand systems studied in this work.

Binding Sites↗
PubMed2005

Evaluation of Poisson solvation models using a hybrid explicit/implicit solvent method.

Implicit solvent methods have become popular tools in the field of protein dynamics simulations, yet evaluation of their validity has been primarily limited to comparisons with experimental and theoretical data for small molecules. In this paper, we use a recently developed hybrid explicit/implicit solvent methodology to evaluate the accuracy of several Poisson-based implicit solvent models. Specifically, we focus on the calculation of electrostatic solvation free energies of various fixed conformations for two proteins. We show that, among various dielectric boundary definitions, the Lee-Richards molecular surface has the best agreement with hybrid solvent results. Furthermore, certain modifications of the molecular surface Poisson protocol provide varied results. For instance, simple modifications of atomic radii on charged residues generally improve absolute errors but do not significantly reduce relative errors among conformations. On the other hand, using a water-probe radius of 1.0 A, as opposed to the standard value of 1.4 A, to generate the molecular surface, moderately improves both absolute and relative results.

Calibration↗
PubMed2005

Cone damage in patients receiving high-dose irofulven treatment.

OBJECTIVES: To describe the clinical, perimetric, and electroretinographic (ERG) results of 4 patients with cone dysfunction following irofulven treatment including the histopathologic and immunocytochemical features of one patient's retinas. DESIGN: Observational case series. METHODS: The patients were examined clinically, including perimetric and ERG evaluations. Eyes from patient 1 and healthy postmortem eyes were processed for histopathologic and immunocytochemistry studies with antibodies specific for cones, rods, and reactive Müller cells. MAIN OUTCOME MEASURES: Clinical signs and symptoms, perimetry, ERG, retinal histopathologic and immunocytochemistry study results. RESULTS: All 4 patients had ERG changes consistent with abnormal cone responses and relatively normal rod responses. Compared with control eyes, the retina of patient 1 had approximately half the normal numbers of macular cones and fewer peripheral cones. The number of rods were normal but all rod and cone outer segments were shortened. CONCLUSION: High-dose irofulven treatment causes cone-specific damage with relative sparing of rods.

Adult↗